There is a multi-junction solar cell that is used as a highly efficient solar cell. The multi-junction solar cell is, for example, a tandem solar cell. There are expectations for the multi-junction solar cell to have a high efficiency compared to a single junction solar cell. On the other hand, a difference undesirably occurs between the current values of each layer if the number of photons absorbed by each layer is different. When the difference between the current values occurs, the conversion efficiency is undesirably limited by the layer having the lowest current value. This is inevitable as long as the layers are connected in series. Conversely, the limit of the conversion efficiency described above can be avoided by drawing out terminals from each layer. However, it is undesirably necessary to provide multiple power converters, etc. It is desirable to increase the conversion efficiency of the multi-junction solar cell.